This invention relates to telecommunications networks and in particular to methods and apparatus for the transmission of traffic to a desired destination.
Conventional telecommunications networks comprise a number of nodes interconnected by transmission paths. A key process in all such networks is that of traffic routing to ensure that signals launched from a network node are transmitted, i.e. correctly routed to a desired destination node. Current techniques for achieving this routing include the use of signalling channels to set up connections or virtual connections across the network, or the use of packet techniques in which each packet has a header containing information from which the destination can be determined. In order to facilitate the routing process, each network node is provided with routing tables from which the correct paths to other network nodes can be determined for traffic arriving at that node. As communications networks increase in size and in their traffic handling capacity, the traffic routing requirement is placing an increasing computational burden on the network operator.
An object of the invention is to minimise or to overcome the above disadvantage.
A further object of the invention is to provide an improved arrangement and method for routing traffic in a communications network.
According to a first aspect of the invention there is provided a communications network, having a plurality of nodes each arranged to extract signals received on orthogonal input paths when there is a predetermined correlation between them, and to retransmit the signals on orthogonal output paths when the predetermined correlation does not exist, each node being further arranged to launch signals intended for a particular other node, on orthogonal paths and with a phase difference such that the signals arrive at the node for which they are intended with the predetermined correlation.
According to another aspect of the invention there is provided a communications network as claimed in claim 1, wherein each node is arranged to analyse data to be transmitted over the network into a plurality of signals (LAPAFs) which are logically analogous to probability amplitude functions (PAFs) to launch in said orthogonal directions, and is arranged to combine probability functions received on orthogonal input paths such that at the intended node the data is reconstructed and at other nodes no signal is constructed.
The correlated extracted signal can be used either to set a network switch position or as a message in its own right.
Local processing of the signals is sufficient to extract a signal intended for a particular node. There is no need for centralised control or the separate transmission of signalling data.
Advantageously, the signals comprise complex signals that are resolved into their orthogonal real and imaginary parts for transmission and are reconstituted at the desired receiving node.
The transmitted signals represent an instantaneous envelope of the cell or bit rate of the information represented by the signal. Typically, the total of the instantaneous cell rates at each part of the network is equal to the pre-assigned capacity for that group of information envelope flows. These groups of information flows can be arranged in a hierarchy so that the summed ate of information flow envelopes is equal to the transmission capacity of each network link.
Preferably, local conservation is applied to the real and imaginary signal components so as to ensure global conservation of information flows. Thus, no flow need be terminated except at the desired exit node.
In a preferred form, each node is arranged to analyse data to be transmitted over the network into a plurality of signals (LAPAFs) which are logically analogous to probability amplitude functions (PAFs) to launch in said orthogonal directions, and is arranged to combine LAPAFs received on orthogonal input paths such that at the intended node the data is reconstructed and at other nodes no signal is constructed. These LAPAFs obey global, and local conservation rules in a manner analogous to PAFs in quantum mechanics. The LAPFs can also represent the instantaneous cell rate and/or bit rate information flow envelope for each information stream.
In that form, one function may be a digital signal representing the complex conjugate of a LAPAF launched in an orthogonal direction.
Most conveniently, the delays in transmission paths between adjacent nodes may each be a respective integer multiple of one of a set of predetermined fixed units. These may be geometrically related to the structure of the network, for example 1, 2 and 5.